My last post, Michaela’s Knowledge Deficit, is proving very popular and has led to a lot of twitter discussion around the issues of qualifications appropriate to subject specialists and desirable standards for mathematical resources. Upon looking at the incorrect diagrams discussed in that post many people, like me, had a WTF moment while others could not quite place their brains on what it was that troubled them about what they saw. I hope in exposing the incorrect nature of one of these mind-bending, eye-twisting blots that I can help readers to understand the long-term implications of not challenging such incorrect material and thus motivate them to greater concern for the standard of maths currently being delivered by some schools and personnel, perhaps even to your own children.